Effect of irrigation with diluted winery wastewater on phosphorus in four differently textured soils
CITATION: Mulidzi, A. R., Clarke, C. E. & Myburgh, P. A. 2016. Effect of irrigation with diluted winery wastewater on phosphorus in four differently textured soils. South African Journal for Enology and Viticulture, 37(1): 79-84, doi:10.21548/37-1-761.
The original publication is available at http://www.journals.ac.za/index.php/sajev
The wine industry needs solutions for wastewater treatment, as environmental legislation for its disposal is increasingly being enforced due to non-compliance. The feasibility of re-using diluted winery wastewater was assessed in a pot experiment under a rain shelter over four simulated irrigation seasons. Four soils varying in parent material and clay content, viz. aeolic sand from Lutzville containing 0.4% clay, alluvial sand from Rawsonville containing 3.3% clay, granite-derived soil from Stellenbosch containing 13% clay, and shale-derived soil from Stellenbosch containing 20% clay, were irrigated with wastewater diluted to 3 000 mg/L COD (chemical oxygen demand), whereas the control received municipal water. Irrigation with diluted winery wastewater increased the pH(KCl) in the shale- and granite-derived soils into the optimum range for P availability. Although pH(KCl) in the aeolic sand was initially above the optimum range, relatively high Na+ levels also caused available P to increase as the pH(KCl) increased. The pH(KCl) in the alluvial sand increased beyond the optimum range, thereby causing a reduction in the available P. This indicates that irrigation with diluted winery wastewater may only enhance P absorption if the pH(KCl) shift is towards the optimum. It must be noted that the results represent a worst-case scenario, i.e. in the absence of rainfall or crops.